Rotor construction for gas turbine engines



April 5, 1960 N. KLOMPAS EI' L ROTOR CONSTRUCTION FOR GAS TURBINE ENGINES .Filed D60. 24, 1956 W MA% mMAB m I ROTOR CONSTRUCTION FOR GAS TURBINE ENGINES Application December 24, 1956, Serial No. 630,383

' 4 Claims. (Cl. 253-39) This invention relates to rotor construction in axial flow gas turbine engines, and it relates more particularly to the construction of the spacing members between adjacent rotor discs in a multiple-stage turbine or compressor. g

In the construction of a multiple stage turbine, for instance, annular rows of blades are'supported on discs spaced axially along and secured to the rotatable shaft of the turbine. Co-operating annular rows of stator blades are secured to shroud rings so as to alternate with the rows of rotor blades, and the stator shroud rings are secured to the turbine outer framework or casing.

In order to maintain proper axial spacing of the rotor discs, it has been found necessary not only to secure them to a central shaft, but also to provide spacing members between them.- These spacing members often take the form of cylindrical or conical rings, located concentrically between adjacent discs. This arrangement not only provides a continuous floor in the annular conduit for the hot working fluid but also gives additional support to counteract axial stress on the rotor discs, which may be due to gas pressure or centrifugal forces. The spacing rings normally co-operate with stationary labyrinth-type seals mounted on the inner ends of the stator blades to provide gas seals between the stages of the turbine.

Known types of spacing rings may take the form of axial extensions of the outer peripheries of the rotor, arranged to abut the peripheries of adjacent rotor discs, or they may be rings secured in position between the discs. In order to provide an eflicient seal between successive stages the clearances between the spacing ringsand the cooperating labyrinth seals must be as small as possible, but in conventional spacing ring constructions, these clearances must be sufliciently large to take into account the fluctuations in diameter caused by extreme temperature variations and by so-called hoop stress encountered at the high rotational speeds employed in turbine engines. The necessary clearances are thus too large to prevent serious gas loss.

The construction according to the invention provides a spacing ring that is less affected by operating temperatures and that substantially resists such hoop stress While efl'iciently supporting the rotor stages axially, and that therefore allows for relatively small clearances between the mating surfaces of the interstage seal, resulting in greater turbine efliciency.

This construction provides a spacing member that is supported radially against hoop stress by the rotor discs themselves, so as to maintain its concentricity at high rotational speeds and reduce vibration.

The spacing ring according to the invention supports and is supported by the rotor discs at a location that is remote from the hot working fluid, thus avoiding adverse heat effects onthe spacing rings.

The invention will now be described with reference to the figures of the drawing in which Fig. l is a side elevation, partly in section showing a ice spacing ring incorporated in a turbine, according to the i invention.

F lg. 2 shows a perspective cross-sectional view of a pre ferred construction of the spacing ring.

A gas turbine engine of otherwise conventional design into which the present invention has been incorporated comprises a two stage-axial flow turbine 1 supplied with working fluid by combustion chambers 2 which are supplied with air by a compressor 3, all enclosed by an outer casing 4. The casing 4 defines the outer wall of the annular conduit through which the but working gases How.

The present invention can be applied to either or both the compressor and the turbine to maintain correct spacing between the rotor discs thereof. but for the purpose of illustration, it is described herein only as applied to the turbine 1, which includes rotor discs 6 with flanged rims 6 supporting on their outer peripheries 7 the rotor blades 8 for rotational movement around the shaft of the turbine.

A torque-carrying inner ring or hub 10 is connected to the rotor discs in any suitable manner, as by brazing, to secure them against rotational movement and axial displacement with respect -to one another. This hub carries an annular web 12, which is integral with and supports a spacing ring 14 provided by cylindrical spacing ring flanges 14 extending axially between the flanged rims 6 of the rotor discs 6. The spacing ring 14 engages the radially-inward-facing surfaces 6 of the rotor disc flanged rims 6 and thus it is spaced radially inward. of the outer peripheries 7 of the rotor discs that partly define the inner wall of the annular conduit for the hot gases. An integral annular web extension 16 extends outward from the ring 14 to a cylindrical rotating sealing ring 18.

Near the end 14 of each spacing ring flange 14 is a radial proiection 14* arranged to abut the opposed face of the adjacent rotor disc flanged rim 6 the ends 14 of the spacing ring flanges and the radial projection 14 form right-angled abutments that receive the adjacent rotor disc rims 6 in radial and axial engagement. The

radially-inward-facing surfaces 6 of the rotor disc rims may be recessed to receive the ends 114 of the spacing ring flanges.

Stator blades 20, which may be conventionally supported on a shroud ring 22 secured to the outer casing 4, co-operate with the rotor blades to complete the two 4 stage axial fiow turbine.

The inner ends of the stator blades 20 are joined by a stationary sealing ring 24 carrying a reinforcing member 26 that is serpentine in cross section. The stationary sealing ring 24 is generally axially aligned with the outer peripheries '7 of the rotor disc flanged rims, and with them defines the inner wall or floor of the annular conduit for the hot gases. To the ring 24 is secured a labyrinth interstage seal 28 that co-operates with the cylindrical surface of the rotatable sealing ring 18; thus, the labyrinth seal is located well below the inner boundary of the hot gases.

The structure is arranged so that the cooling air normally used to cool the engine bearings and other parts can be passed over the stressed parts of the spacing ring construction. For this purpose, holes 30, 32 and 34 are provided in the rotor discs 6, in the web 12 and in the spacing ring 14, respectively, to transmit the cooling air over the spacing ring-structure.

The construction described provides a rotating spacing ring and seal structure that is substantially immune to hoop stress and other rotational disturbances, and that p aces the stressed parts in areas that are not only remote from the region occupied by hot gases but that also can be conveniently cooled by a flow of cooling air,

While a preferred embodiment of the invention has been described, it is to be appreciated that modifications and alterations may be madewithin the spirit and scope of this invention as defined in thefollowing claims.

What we claim as our invention is:

1. A spacing ring structure for a multiple-stage gas turbine or compressor comprising an outer casing, a pair of axially spaced-apart rotor discs, a row of rotor blades on the outer periphery of each of the rotor discs, a row of stator blades supported by the casing and located between the rows of rotor blades, the rotor discs having flanged rims providing radially-inward-facing surfaces spaced radially inward of the outer peripheries of the rotor discs, a hub joining and secured to the rotor discs radially inward of the said surfaces, an annular web extending radially outwardfrom-the hub; a" spacing ring provided by cylindrical spacing ring flanges extending co-axially from the opposite faces of the said web to the rotor discs and engaging the said radially-inward-facingsurfaces, an annular extension of the said web extending radially beyond the said spacing rin a cylindrical rotating sealing ring on the outer periphery of the said web extension, a cylindrical stationary sealing ring joining the radially inner ends of the stator blades and in substantially axial alignment with the outer peripheries of the rotor discs, and gas-flow-sealing means between the rotating and the stationary sealing rings.

2. A spacing ring structure for a multiple-stage gas turbine or compressor comprising an outer casing, a pair of axially spaced-apart rotor discs, air-conducting holes in the said discs, the outer peripheries of the discs being spaced from the outer casing to provide an annular conduit for hot gases, a row of rotor blades on the outer periphery of each of the rotor discs, a row of stator blades extending radially inward from and fastened to the casing between the rows of rotor blades, a cylindrical stationary sealing ring joining the radially inner ends of the stator blades and in substantially axial alignment with the peripheries of the rotor discs and with them defining the inner wall of the annular conduit, the rotor disc's having'flanged rims at their outer peripheries each providing a radially-inward-facing bearing surface spaced radially inward of the outer periphery of the corresponding rotor disc, a hub joining and secured to the rotor discs radially inward of the said surfaces, an annular web extending radially outward from the hub and having air-conducting holes therein, a spacing ring provided by cylindrical spacing ring flanges extending co-axially from the opposite faces of the said web to the rotor discs and engaging the aforesaid bearing surfaces, each of the spacing ring flanges having air-conducting holes therein, an annular extension of the said web extending radially beyond the said spacing ring, a cylindrical rotating sealing ring encircling the web extension, and a labyrinth-type seal between the rotating and the stationary sealing rings.

3. A spacing ring structure fora multiple-stage gas turbine or compressor comprising an outer casing, a pair of axially spaced-apart rotor discs,a row of rotor blades on the outer periphery of each of the rotor discs, a row of stator blades supported by the casing and located between the rows of rotor blades, the. rotor discs having flanged rims providing radially-inward-facing surfaces spaced radially inward of the outer peripheries of the rotor discs, a hub joining and secured "to the? rotor discs radially inward of the said surfaces, an annular web extending radially outward from the hub, a spacing ring provided by cylindrical spacing ring flanges extending coaxially from the opposite faces of the said web to the rotor discs and engaging the said radially-inward-facing surfaces, a generally radial projection on each of the spacing ring flanges abutting the opposed face of the adjacent rotor disc, an

annular extension of the aforesaid web extending rarotor discs, and gas-flow-sealing means between the rotating and the stationary sealing rings.

4. A spacing ring structure for a multiple-stage gas turbine or compressor comprising an outer casing, a pair of axially spaced-apart rotor discs, a row of rotor blades on the outer periphery of each of the rotor discs, a row of stator blades supported by the casing and located between the rows of rotor blades, the rotor discs having flanged rims providing radially-inward-facing surfaces spaced radially inward of the outer peripheries of the rotor discs, a hub joining and secured to the rotor discs radially inward of the said surfaces, an annular web extending radially outward from the hub, a spacing ring provided by cylindrical spacing ring flanges extending coaxially from the opposite faces of the said web to the rotor discs'and engaging the said radially-inward-facing surfaces, a generally radial projection near the end of each spacing ring flange and providing in conjunction with the end of the flange a right-angled abutment that receives the adjacent rotor disc rim in radial and in axial engagement, an annular extension of the aforesaid web extending radially beyond the said spacing ring, a cylindrical rotating sealing ring on the outer periphery of the said web extensions, a cylindrical stationary sealing ring joining the radially inner ends of the stator blades and in substantially axial alignment with the outer peripheries of the rotor discs, and gas-flow-sealing means between the rotating and the stationary sealing rings.

References Cited in the file of this patent UNITED STATES PATENTS 2,452,782 I McLeod Nov. 2, 1948 2,557,747 Judson June 19, 1951 2,657,901 McLeod Nov. 3, 1953 2,793,832 Wheatley May 28, 1957 FOREIGN PATENTS 706,730 Great Britain Apr. 7, 1954 724,281 Great Britain Feb. 16, 1955 

